Field of the Invention
The present invention relates to a terminal for a mobile communication.
Related Art
Mobile communication technologies has evolved through 2G and 3G into 4G.
FIG. 1 illustrates a mobile communication system.
As illustrated in FIG. 1, a mobile communication system includes at least one base station (BS) 20. Each base station 20 provides a service to terminals 10 existing in specific geographic areas (which are, in general, called cells) 20a, 20b, and 20c. 
The advancement of mobile communication technologies has enabled data to be wirelessly transmitted and received at high speeds.
Further more, the terminals 100 goes beyond a regular phone which provides only a phone-call function, and has evolved into a smart phone which provides various functions, therefore improving User Experience (UE).
Meanwhile, many efforts have been being made recently to study and research a Machine Type communication (MTC) or an Internet of Things (IoT) which enables communication between devices and devices or between a device and a server without human intervention. The MIC or the IoT is a concept of communication by a machine device, other than a terminal used by a human, over a wireless communication network. Such an MTC or IoT can be used in various fields, such as tracking, metering, payment, medical industries, and remote control techniques.
A device for the MTC or the IOT transmits a small amount of data, and sometimes needs to transmit and receive uplink/downlink data.
Considering the above characteristics, Wideband Code Division Multiple Access (WCDMA), which is the 3G mobile communication, may be used for the MTC or the IoT and reduce the costs of the device and battery power consumption.
One of the important characteristics of Code Division Multiple Access (CDMA), on which the WCDMA is based, is a rake reception function. The rake reception function is a function of separating two signals according to time delay, the signals which are transmitted at the same time from a base station but arrive a receiver at a different points in time (that is, with phase difference) due to multi-path fading. For this reason, time synchronization is critical for the rake reception function. If a timing offset occurs due to asynchronous time, it may result in degradation of performance.
Accordingly, a WCDMA receiver performs oversampling in order to reduce a timing offset. However, if a timing offset of ⅛ chip occurs when four-times oversampling is performed, it is not possible to compensate for it. To reduce the timing offset of ⅛ to ½ chip, it may be possible to increase the oversampling rate twice to perform 8-times oversampling, but it could also increase complexity considerably. In addition, even when 8-times oversampling is performed, it is still not possible to overcome a timing offset of 1/16 chip.
In sum, increasing an oversampling rate results in an increase in complexity and memory usage. Thus, it is not a perfect solution and fails to overcome a timing offset 1/(an oversampling rate*2).